Methods of preparing single-walled carbon nanotube networks
Methods for determining desired doping conditions for a semiconducting single-walled carbon nanotube (s-SWCNT) are provided. One exemplary method includes doping each of a plurality of s-SWCNT networks under a respective set of doping conditions; determining a thermoelectric (TE) power factor as a function of a fractional bleach of an absorption spectrum for the plurality of s-SWCNT networks doped under the respective sets of doping conditions; and using the function to identify one of the TE power factors within a range of the fractional bleach of the absorption spectrum. The identified TE power factor corresponds to the desired doping conditions.
1. A method for estimating the maximum thermoelectric (TE) power factor for a semiconducting single-walled carbon nanotube (s-SWCNT) network, the method comprising, in order:
determining an undoped absorption value (A 0 ) by:
measuring a first absorption spectrum for the s-SWCNT network in an undoped state;
determining the location of at least one of a first excitonic peak envelope (S 11 ) or a second excitonic peak envelope (S 22 ) in the first absorption spectrum; and
integrating the first absorption spectrum between a range that includes at least one of S 11 or S 22 to obtain A 0 ;
determining a doped absorption value (A i ) by:
measuring a second absorption spectrum for the s-SWCNT network for at least three different doping levels;
integrating the second absorption spectrum for each of the doping levels between the range to obtain at least three values for A i ; and
measuring an electrical conductivity for each of the doping levels;
calculating for each of the doping levels:
a difference of A 0 −A i ; and
a fractional bleach value defined as (A 0 −A i )/A 0 ;
creating a plot of the electrical conductivity versus the fractional bleach value for each of the doping levels; and
determining a transition fractional bleach value corresponding to a change in slope of the plot, wherein:
the transition fractional bleach value corresponds to an optimum doping level for providing the maximum TE power factor.
2. The method according to claim 1 , wherein the at least three doping levels are achieved by:
immersing the s-SWCNT network in a solution comprising a charge-transfer dopant until a charge carrier doping level of the s-SWCNT network is saturated; and
subsequently reducing the charge carrier doping level of the s-SWCNT network.
3. The method according to claim 2 , wherein the charge-transfer dopant comprises triethyloxonium hexachloroantimonate (OA).
4. The method according to claim 1 , wherein the at least three doping levels are achieved by sequentially immersing the s-SWCNT network in solutions comprising increasing concentrations of a charge-transfer dopant.
5. The method according to claim 4 , wherein the charge-transfer dopant comprises triethyloxonium hexachloroantimonate (OA).
6. The method according to claim 1 , wherein the range is between 650 nm and 2400 nm, inclusively.
7. The method according to claim 1 , wherein the s-SWCNT network comprises s-SWCNTs having a diameter between 0.8 nm and 1.8 nm, inclusively.
8. The method according to claim 1 , wherein the transitional fractional bleach value is between 0.43 and 0.61, inclusively.
9. The method according to claim 1 , wherein:
the change in slope is at an intersection of a first line and a second line,
the first line has a slope between 42,000 S/m and 112,000 S/m, inclusively, and
the second line has a slope between 195,000 S/m and 787,000 S/m, inclusively.
10. The method according to claim 1 , wherein the maximum TE power factor is between 139 μW m −1 K −2 and 349 μW m −1 K −2 , inclusively.